An interface standard called IEEE 1394 has recently been attracting much attention. This IEEE 1394 has standardized high-speed serial bus interfaces that can handle the next generation of multimedia devices. IEEE 1394 makes it possible to handle data that is required to have real-time capabilities, such as moving images. A bus in accordance with IEEE 1394 can be connected not only to peripheral equipment for computers, such as printers, scanners, CD-R drives, and hard disk drives, but also to domestic appliances such as video cameras, VTRs, and TVs. This standard is therefore expected to enable a dramatic acceleration of the digitalization of electronic equipment.
The concept of IEEE 1394 is disclosed in various publications, such as “An outline of the IEEE 1394 High Performance Serial Bus” (Interface, April 1996, pages 1 to 10), “Bus Standards for PC Peripheral Equipment” (Interface, January 1997, pages 106 to 116), and “Real-Time Transfer Modes and Multimedia-Capable Protocols for IEEE 1394-1995 (FireWire)” (Interface, January 1997, pages 136 to 146). Texas Instruments' TSB12LV31 is known as a data transfer control device that conforms to IEEE 1394.
However, some technical problems have been identified with such a data transfer control device conforming to IEEE 1394, as described below.
That is to say, the current IEEE 1394 standard does make it possible to implement transfer speeds up to a maximum of 400 Mbps. In practice, however, the presence of processing overheads forces the actual transfer speeds of the entire system to be much slower. In other words, the firmware and application software running on a CPU require large amounts of time for processes such as preparing for transmitting data and reading in received data, which means it is not possible to implement high-speed data transfer overall, no matter how fast the data can be transferred over the IEEE 1394 buses.
A particular problem lies in the fact that a CPU incorporated into peripheral equipment has a lower processing capability than the CPU incorporated into the host system, such as a personal computer. This makes the problem of processing overheads in the firmware and application software extremely serious. It is therefore desirable to provide techniques that are capable of efficiently solving this overhead problem.